$ du -sh

For example, on my MacBook Pro when I execute this command in my home directory, I get something like so:

danbookpro:~ daniel$ du -sh
 53G    .

Very good then. Carry on.

Update

If you’re looking for a real good time, give this a try (thanks Nick):

du -chs ~/*

This will give you a list of each file/directory and the amount of disk space used by each. In my case something like this:

danbookpro:~ daniel$ du -chs ~/*
 58M    /Users/daniel/Bin
853M    /Users/daniel/Desktop
1.3G    /Users/daniel/Documents
1.1M    /Users/daniel/Droplets
 10G    /Users/daniel/Library
 25M    /Users/daniel/Movies
7.2G    /Users/daniel/Music
 26G    /Users/daniel/Pictures
1.5G    /Users/daniel/Public
112K    /Users/daniel/Sites
6.2G    /Users/daniel/Work
 53G    total
danbookpro:~ daniel$